For example, for use in hard disk drive devices as external memory devices for computers, attention has been directed in recent years to thin film magnetic heads of the composite type which comprise an inductive head element for recording signals and a magnetoresistance effect head element (hereinafter referred to as an "MR head element") for reproducing signals.
U.S. Pat. No. 5,438,747 discloses a composite-type thin film magnetic head, the structure of which is shown in FIG. 67, FIG. 68 (section taken along the line A--A in FIG. 67), FIG. 69 (section taken along the line B--B in FIG. 67) and FIG. 70 (section taken along the line C--C in FIG. 67). An upper insulating layer 72 and protective layer 12 are not shown in FIG. 67 for the sake of convenience.
The composite-type thin film magnetic head includes an MR head element comprising a lower shield layer 2, lower insulating layer 31, MR element layer 4, electrode layer (not shown) and upper insulating layer 32 which are successively formed as superposed on a substrate 1.
Provided on the MR head element is an inductive head element comprising a lower core layer 5, gap spacer layer 6, lower insulating layer 71, coil layer 8, upper insulating layer 72 and upper core layer 90 which are successively formed as superposed layers.
The lower core layer 5 comprises a shield layer 51 formed on the substrate (1) side thereof and having a large width, and a core layer 52 formed on the other side thereof and having a small width equal to the track wide on recording media in the vicinity of the face to be opposed to the medium. The core layer 5 serves the function of the magnetic core of the inductive head element and also performs the function of a magnetic shield between the inductive head element and the MR head element.
The upper core layer 90 comprises a first core layer 901 in the form of a thin film and formed on the substrate (1) side thereof, and a second core layer 902 in the form of a thick film and formed on the other side thereof. These first and second core layers 901, 902 have the same width as the track width in the vicinity of the medium-opposed face. As shown in FIG. 68, the core portion 52 of the lower core layer 5, gap spacer layer 6, first core layer 901 and second core layer 902 are aligned with one another on a vertical plane at each of opposite sides with respect to the direction of the track wide.
A protective layer 12 is formed over the MR head element and the inductive head element.
In producing the composite-type thin film magnetic head described, the upper core layer 90 is formed by plating with use of a resist frame, and the core portion 52 of the lower core layer 5 is thereafter formed by ion beam etching with the upper core layer 90 serving as a mask.
Alternatively, the core portion 52 of the lower core layer 5 and the upper core layer 90 can be formed at the same time by ion beam etching with use of a resist layer.
With the magnetic head of the type described, a large stepped portion C3 is formed between the surface of the gap spacer layer 6 and the surface of the upper insulating layer 72 as seen in FIG. 69. In fabricating the magnetic head, a resist frame or resist layer is provided on the stepped portion C3 to form the upper core layer 90.
However, it is difficult to accurately form the resist frame or resist layer on such a large stepped portion C3, and it is impossible to form the resist frame or layer in a predetermined configuration. The accuracy of the resist frame or layer formed is still lower especially in fabricating composite-type thin film magnetic heads having a reduced track width of up to 3 micrometers so as to achieve a higher recording density.
As a result, it is impossible to obtain an upper core layer of contemplated width and to obtain an accurate track width. This gives rise to the problem that the production process achieves a lower yield.
The present applicant has disclosed the technique of forming an upper core layer by ion beam etching with use of a double-layer resist in JP-A-161222/1997, whereas a great stepped portion is formed also in this case as is the case with the magnetic head described above, so that the double-layer resist formed is low in accuracy, a double-layer resist of specified configuration still remains to be obtained.